This invention relates to pipeline pig launching systems, and more particularly to diver assisted systems for launching pigs into subsea pipelines.
In the oil and gas industry a common procedure for removing petroleum deposits and other debris from pipelines is to push a scraper, referred to as a "pig", through the lines by fluid pressure. The pig is introduced into the pipeline from a launching system generally comprising a housing for the pig, a pipe reducing nipple, a launching valve, and a source of fluid pressure connected to the housing behind the pig. The diameter of the pig prior to launching is greater than that of the pipeline so that considerable force is required to seat the pig against, and move it through, the reducing nipple. It is at this point where conventional pig launching systems fail unless the pig is loaded properly so that it seals against the pipe wall near the reduced neck portion of the reducing nipple. Some physical or mechanically assisted effort on the part of the operator is often required to compress the pig to achieve a proper seal, thereby frequently presenting a problem that is compounded underwater where a diver may not have the strength or mobility to properly install the pig.